Monday, October 5, 2009

Aerospace Engine situation with the big transport

As you guys all know, the biggest problem that PLAAF have always had is the lack of high performing engine series. J-10 still relies on AL-31FN. We didn't see any new J-10s for a while, because they used up all of the AL-31FNs. J-11B used WS-10A for a while, but had so much problems that many of them are also using AL-31F. H-6K project was basically stopped, because the suspension of the contract for 240 D-30KP2. J-10 and H-6K production basically only restarted recently because China started to purchase engines from the Russians again. Similarly, the L-15 project has been delayed and Z-10 project has been delayed. Of all the project, I think the one that is the most important for PLAAF and has suffered the most is the large transport project. It's quite apparent that PLAAF needs something in the class of D-30KP2 to equip not only the large transport but also H-6K, newer variants of H-6 and possible future bomber projects. We all know about the tremendous need for large transport in PLAAF. They basically can't build newer KJ-2000 units, because they are running so low on IL-76 airframes.

Having said all of this. It appears that the prototypes and first batch of the large transport will be using D-30KP2 or the domestic version WS-18. WS-18 is being produced by ChengFa group (Website). Chengdu engine group (aka Factory 420) is also tasked with license production of L-15's engine AI-222-25F. People will ask why they are depending on something so old (China has had access to it since the 80s when they imported Tu-154). The truth is that PLAAF just needs something that works. D-30KP3 at this point is still not ready for mass production, so they have to go with KP2. PS-90A is a possibility, but PLAAF is going for the cheaper option for purchase and license production (or possibly unlicensed production). Therefore, WS-18 is pretty much just going to be the domestic version of D-30KP2, although maybe slightly improved in fuel efficiency and such. This engine was said to have had its first flight in January of 2007, so it should be ready for the large transport when it makes its first flight in 2012. It will probably ready even earlier for H-6K, H-6U and other variants of H-6.

On top of WS-18, there is also a high bypass turbofan engine under development with its core based on WS-10A. It will eventually be the engine used to power the large transport. I think a variant of it will probably also be pitched as the engine for C919. Now, we all thought that Shenyang Liming (606 Institute) was going to be developing it, but we found out recently that the work has been given to Xi'an AeroEngine (410 Institute). In many ways, it does make sense for XAEC to develop/produce this engine, because Xi'an is also the home of XAC/SAC, which is in charge the large transport project. However, Shenyang Liming is the developer of WS-10A and follow-up variants, so it's unusual for the large bypass variant of the engine to be given to someone else. At this point, Liming still has WP-14 Kunlun series, WS-10A Taihang series, a bunch of domestic gas turbines (QC-70, QC-128, QC-168, QC-185 and QC-260). We all know about the troubles in the WS-10A, but I've read that the Kunlun series also have had a lot of problems. Amongst all the major gas turbine projects, only QC-70 and QC-128 are ready for production. XAEC is now working on WS-9, WS-15, 1/3 of the production work for WS-10A, the large bypass turbofan engine for large transport and most of the production for QC-280. As the result of this, XAEC will be responsible for the future power plant of JH-7A, 5th gen fighter, large transport/special mission aircraft and major warships and also be very instrumental in the power plant of J-10 and J-11. A few years ago, it seemed that Liming was becoming the dominant engine maker in China due to its role in Kunlun and Taihang series, which were the 2 most important aerospace engine projects at that time (and possibly still are). However, due to its failure in those 2 projects and delays in the gas turbine projects, it has really lost out to XAEC, which performed well with WS-9 and QC-280. I think the shift of this extremely high profile project is a sign that PLA is really unhappy with Liming.

Anyhow, there is a really good article written by SAERI (Shenyang AeroEngine Research Institute). It talks about the 2 engine possibilities (WS-18 and the one based on WS-10) that could be used to power a domestic large transport. The engines are designed to be comparable to D-30KP2 in size/dimension. China has two previous attempts at medium to large turbofan engine. WS-5 from the 60s had a bypass ratio of 1.49 and WS-6 had a bypass ratio of 1.85. Comparatively speaking, D-30KP2 has a bypass ratio of 2.42 while a modern airliner engine like CFM-56-5A has a ratio of 6 and PS-90A has a ratio of 4.6. In this article, SAERI put out to proposals:

WS-Y1 (I guess WS-18 here) that has the same dimension as D-30KP2, with the same thrust, but slight improvement in the bypass ratio

WS-Y2 (the one based on WS-10) that has slightly different ratio, with the same thrust, but bigger improvement in the bypass ratio

In the analysis, they believe that the air consumption of Y1 would be 285 kg/s and of Y2 would be 380 kg/s. That will produce bypass ratio of around 3 for Y1 and 5 to 6 for Y2. The fan diameter of Y1 would be 1460mm like it is for D-30KP2 and 1700 mm for Y2. The thrust at takeoff mode would be the same for Y1 and Y2 as it is for D-30KP2 (12000 kgf). At an altitude of 11000 m and speed of mach 0.8, the fuel consumption rates would be 0.67-0.68 for Y1 and 0.6-0.62 for Y2 compared to 0.7 for D-30KP2 and 0.595 for PS-90A. And the takeoff fuel consumption rates would be 0.45-0.48 for Y1 and 0.35-0.38 for Y2 compared to 0.51 for D-30KP2.

Unfortunately, it's hard to verify how close these figures would be to the engines that get developed. However, due to the fact that this was written by SAERI which basically developed the engines that are now being produced by Shenyang Liming, I think the published numbers should not be that far from the truth. It looks like they have achieved much better fuel consumption numbers than D-30KP2, but still trails PS-90A and obviously the latest variants of CFM-56. Something along the line of Y2 is more than enough for China's large transport needs. However, I find it curious that they think they can develop a domestic engine option that can compete against next generation Western options (like PW's GTF series), when it would likely be inferior to CFM-56-7 series.

The order for 240 D-30KP2 made in 2005 is finally getting carried out this year. These engines might all be delivered by 2012. I think China chose this ahead of KP3 and PS-90A due to maturity of the engine, its lower cost and not wanting to support two lines of high-bypass Russian turbofan engines. By that time, WS-18 should be more than ready to be equipped. WS-10-118 (which is the code name for the large bypass engine prototype based on WS-10A) will probably be ready 3 or 4 years later for the domestic large transport project. WS-18 will still be produced at that point to service the existing fleet using D-30KP2 engines.

generally speaking, it's a reliability issue. Which seems to have ben prevalent in the ones that are being mass produced. It could be an issue with the initial design and/or an issu with the process of mass production.

Feng, thanks for answering my question. Do you have a public source for the issues that you talked about? I'm very curious about the nature of these issues. The US and UK have been mass producing similar engines with very high reliability in the past few decades. Perhaps Chinese industry is still lagging very much in the basic science like material sceince and metalurgy?

If it's taking this long for the WS-10A to get into full service with the J-11B and J-10, I don't want to think how long it'll take for the WS-15 to get fully in service with the 5th generation plane...

Well, they do have options, like upgraded variants of WS-10A by then to use. WS-15 is actually proceeding okay from all I have read. It should be ready whenever the 5th gen fighter comes out for at least limited trials. I don't think it will come to this, but they could also buy engines from the Russians if all else fails.

Feng, I am glad that the newer engines are being developed by someone else not Liming. Basically from what I have known. Liming won the projects due to some political reason even those it is pretty incompotent. Just like Sheng Yang Air corp, almost got to develope J-10(Thank Buhhda they did not). Otherwise it will most likely fail as well.

Feng, I think it will be nice that if Sheng Yang Air corp and Chendu Air corp forge into one, like Lockeed Martain. That way the performence of these two companies will be better.

That's the thing. It's never a good idea to only have one design bureau, because then it knows it will get the ocntract regardless. Then, it will get lazy and not come up with good proposals. If you have two, then the air force can say, if we don't like your design, we can go to someone else. That's why you always want competition. And, I hope that the management in SAC and Liming gets better, so they can push CAC and XAEC to improve.

Feng you are right. But in the past politic comes in to bussiness which is not a good thing. SAC is a northern city close to Bejing that is why it got the contract.

However, I think CAC is better than SAC cause it is a western city company and was somewhat discriminated that is why it works harder to get contracts. Just like in America. Asians are discriminated that is why we worker hard and get into great School at HUGE percentage even thoug we are only 4%.